1. Field of the Invention
The present invention relates to a nib for use with fountain pens and other writing instruments and to a method of manufacturing the same. The present invention also relates to a composite conical nib made from a ceramic material with excellent durability.
2. Description of Prior Art
Writing instruments such as fountain pens have conventionally been using nibs with high durability. In the case of a fountain pen, a nib is tipped with a wear-resistant alloy by fusing, formed with a slit and polished at corners to round a tip of the nib. As an example of such a conventional nib, a conical nib is shown in FIG. 1. In FIG. 1 reference numeral 100 represents a nib comprising a nib base body 200 molded of a resin and having a predetermined thickness and a converging member 300.
The nib base body 200 is integrally molded of a synthetic resin material by injection molding and, as shown in FIG. 2, has a cylindrical base portion 201 and a plurality of combtooth pieces 202 protruding from one end of the base portion 201. These combtooth pieces 202 are arranged along a circumference, centered at a center axis of the nib, at equal intervals with a slit 203 formed therebetween. The base portion 201 has a large-diameter portion 211 and a small-diameter portion 212 with a stepped portion 213 formed at a boundary between them. The combtooth pieces 202, each shaped like an arc in cross section, protrude continuously from one end of the large-diameter portion 211 of the base portion 201 and progressively taper off toward the front end. A base portion-side half of each combtooth piece 202 extends almost linearly along an outer circumferential surface of the large-diameter portion 211 and a front end-side half tilts inwardly so that the combtooth pieces 202 progressively approach the center axis toward the front end. The combtooth pieces 202 as a whole are brought closer together inwardly by urging them from their outer circumference toward the center axis. That is, the base end side halves are combined together in a virtually cylindrical shape and the front end side halves in a virtually conical shape. The combtooth pieces 202 have hemisphere-divided portions 204 at their front ends which, when brought together, form a hemisphere. The hemisphere-divided portions 204 are rounded at their outer corners.
The converging member 300, as shown in FIG. 1, is formed into a cylinder that can be fitted over an intermediate portion of the nib base body 200. The converging member 300 has an inner circumferential structure adapted to press the combtooth pieces 202 toward the center axis to converge into a conical shape that progressively decreases in diameter toward the front end.
The nib 100 has the nib base body 200 and the converging member 300 of the above construction as constitutional elements. The converging member 300 is sleeved over the nib base body 200 from its front end and snugly fitted over the circumference of the nib base body 200, so that the inner circumferential structure of the converging member 300 presses the combtooth pieces 202 from outside toward the center axis. Under a uniform pressure of the converging member, the base end side halves converge into an almost cylindrical geometry without distortion and the front end side halves also converge into an almost conical geometry without distortion whose diameter progressively decreases toward the front end. As a result, the adjoining combtooth pieces 202 engage with each other, bringing together the hemisphere divided portions 204 at their front ends to form a smooth hemisphere writing tip 400 with no undulations. In this condition, ink feeding paths 500, capillary-like gaps, are formed between side interfacing portions of the combtooth pieces 202.
In the nib 100 constructed as described above, when the semispherical writing tip 400 is pressed against a surface of writing paper with the pen axis at an angle, the hemisphere divided portions 204 at the free ends of the combtooth pieces 202 slip relative to each other and elastically deform to enlarge an outer diameter of the hemisphere portion at the tip. When the pressing force is removed, the tip of the nib restores its original shape by its elasticity. This behavior allows the nib to write on a paper surface in any direction and, even if the nib is rotated about the pen axis, to write at any position on the hemispherical tip portion and at any angle. Further, the thickness of a line can be changed by adjusting a writing pressure, permitting the writer to write a variety of modes of letters with a changing line width, such as those produced by a writing brush.
The conventional conical nibs, however, have the following problems.
(1) Since the nib base body is molded in the form of a set of combtooth pieces that together have a conical shape, it has a complex geometry, making molding dies complex and expensive and rendering a mass production impossible.
(2) Since the nib base body is molded in the form of a set of combtooth pieces that together have a conical shape, a check to see whether each of the combtooth pieces has a predetermined dimensional accuracy can only be made after the combtooth pieces are assembled into a final product as by fitting a ring over them.
(3) To give a smooth writing feel requires rounding outer surface corners of the tip portion. The outer surface corners are rounded as by a barrel polisher. During this process, the combtooth pieces interfere with each other at slit portions, making it necessary to check that the rounding is being carried out as desired in the middle of the process. This degrades an efficiency of the chamfering or rounding work.
(4) To make the nib of the pen a final product after the rounding operation requires fitting a ring (converging member) over the nib front end portions divided like combteeth. An attempt to perform this ring fitting operation by using an automated assembly machine results in the combtoothlike molded pieces of the nib base body interfering with each other at slit portions and the nib base body failing to rest in its place on an automated feeding apparatus such as a parts feeder. The ring fitting operation must therefore be done manually.
Of the conventional nibs described above, ceramic nibs are drawing attention as highly wear-resistant nibs. Examples of ceramic nibs are disclosed in Japanese Utility Model Disclosure Nos. 60-8085, 60-109979 and 1-86578, and Japanese Patent Disclosure No. 1-146797. Some of the proposed ceramic nibs of this kind have a construction in which a nib body of ceramic plate is formed with a slit and has its tip rounded or in which a barlike nib body is formed with a longitudinal through-hole as an ink feeding hole to supply ink to the tip.
The conventional ceramic nibs, however, has the following drawbacks. Although the ceramic nib has a groove or through-hole for feeding ink, since it is hard and cannot deflect as can a platelike stamped metal nib, the groove or through-hole cannot deal with a change in ink viscosity or with ink scum, resulting in an interruption of ink feed. Further, fine dirt and paper dust produced by contacts between the writing tip of the nib and a paper surface may clog an ink path in the nib body. If that happens, since the nib has almost no provisions for cleaning, the writing performance inevitably becomes unstable. These problems are a major reason that the ceramic nibs, though they use a wear-resistant material, have not been put to practical use and that pens using a ceramic nib have not been able to be marketed as practical writing instruments.
According to one aspect of the present invention, there is provided a conical nib having a plurality of independent combtooth pieces which can converge progressively toward the front ends thereof and combine to form a virtually conical shape over the entire length and a virtually spherical shape at the front ends. These combtooth pieces are each shaped like a pointed knife and their base end portions are used as fixed portions to be inserted into the holding member for fixing. The holding member is formed almost cylindrical and has at one end face thereof groove-shaped fixing portions into which the fixed portions of the combtooth pieces can be axially inserted, and the combtooth pieces are inserted into the fixing portions of the holding member to arrange the base end portions along a circumference. Further, the nib has a converging member which can be fitted over an outer circumference of the combtooth pieces arranged along the circumference by the holding member and which presses the combtooth pieces inwardly from outside to converge them. A plurality of combtooth pieces are assembled by the holding member and the converging member into a conical nib having a writing tip at the front end thereof and an ink feeding path between each combtooth piece.
With this arrangement, the conical nib can be simplified in structure, greatly improving its productivity and realizing a substantial cost reduction.
Another aspect of the present invention provides a method of manufacturing a conical nib which comprises the steps of: forming a plurality of separated combtooth pieces, the combtooth pieces being able to be converged generally into a virtually conical shape, the combtooth pieces having front ends that combine to form a virtually spherical shape; forming a holding member having groove-shaped fixing portions into which base end portions of the plurality of combtooth pieces can be inserted, the holding member being able to arrange the base end portions of the combtooth pieces along a circumference; and forming a converging member capable of being fitted over an outer circumference of the combtooth pieces arranged along the circumference by the holding member to converge the plurality of combtooth pieces; inserting the plurality of combtooth pieces into the fixing portions of the holding member to fix them along the circumference; and fitting the converging member over the outer circumference of the plurality of combtooth pieces to converge the combtooth pieces.
With this manufacturing method, it is possible to automate step of, after the constitutional parts of the conical nib have been prepared, inserting the plurality of combtooth pieces into the fixing portions of the holding member for fixing and a step of fitting the converging member over the outer circumference of the plurality of combtooth pieces. This greatly improves the productivity of the conical nib and also realizes a substantial cost reduction.
Because of the improvements made on the conical nib structure and on the manufacturing process thereof as described above, the present invention offers the following effects and advantages.
Since the shape of the product is simplified, the cost of dies can be reduced to about one-half the conventional one.
The conventional molding process requires a large and strong press. The improvement of the conical shape enables the use of a small press, which in turn reduces the facility cost.
The nib of the conventional construction can only be manufactured at the rate of 150-200 nibs per minute at most. The adoption of the nib construction of this invention increases the rate of production to 5,000 nibs per minute (5 nibs as one set), which is five times the conventional production rate, resulting in a significant reduction in the production cost.
Since the combtooth pieces of the nib are formed as single, separate parts, the dimensional accuracy can easily be checked, preventing faulty parts from getting into the production line.
Since the combtooth pieces of the nib are individually subjected to the process of chamfering or rounding the outer surface corners of the front end of each combtooth piece, the problem of the combtooth pieces interfering with one another is eliminated, enabling a large quantity of nibs to be manufactured in a short period of time. Furthermore, the assembly of individual combtooth pieces can be done by using an automated feeding apparatus, such as parts feeder, thus realizing a substantial cost reduction.
Still another aspect of the present invention provides a ceramic composite conical nib which comprises: a nib base body having a cylindrical base portion, a plurality of combtooth pieces formed at one end of the base portion along a circumference, centered at a center axis thereof, the combtooth pieces being able to converge progressively toward front ends thereof and combine to form a virtually conical shape, and a plurality of hemisphere-divided portions formed at the front ends of the combtooth pieces, the hemisphere-divided portions being able to converge and combine to form a virtually hemispherical tip portion; and a converging member formed cylindrical and being able to be fitted over an outer circumference of the nib base body to converge the plurality of combtooth pieces and the hemisphere-divided portions thereof; wherein each of the combtooth pieces has a front piece on a front end side thereof including the hemisphere-divided portion and a rear piece on a rear end side thereof; wherein the front piece is formed from a ceramic material; wherein the rear piece is formed elastically deformable from a synthetic resin or metal material; wherein the nib base body is converged by the converging member to form an ink feeding path between each combtooth piece and also form a spherical writing tip at a front end thereof.
With this construction, since the tip of the nib is formed of a ceramic material, not only can the tip have a high wear resistance and therefore an enhanced durability but it can also offer a smooth writing feel and produce smooth written lines. Further, because the hemisphere-divided portions of the writing tip shift relative to one another and as a whole deform elastically as a result of elastic deformations of the rear pieces according to the writing pressure applied, the writing tip of the nib, though made of a hard ceramic material, can prevent an interruption of ink feed which would otherwise be caused by an ink viscosity change due to drying of ink or by dried ink scum. Further, if dirt or paper dust adheres to ink paths, the above-described behavior of the writing tip can reliably remove it, assuring a stable writing action. Furthermore, the elastic deformation of the writing tip offers a soft paper-contacting feel and allows the nib to write at any angle to a paper surface and, even if the nib is rotated about the pen axis, at any position on the hemispherical tip portion. It is also possible to draw a line thick or thin by adjusting the writing pressure.
The characteristic features of the present invention may be summarized as follows.
First, the number of combtooth pieces of the nib base body is set to five to eight.
Second, the base portion and the rear piece of each combtooth piece are integrally formed from a synthetic resin or metal material.
Third, one of engagement surfaces of the front piece and the rear piece is provided with an engagement projection and the other engagement surface with an engagement recess. The engagement between these engagement projection and recess connects the front piece and the rear piece.
As described above, since the tip of the nib is made from a ceramic material, the tip has high wear resistance and durability and offers a soft writing feel and produces smooth written lines. Further, because the hemisphere-divided portions of the writing tip shift relative to one another and as a whole deform elastically as a result of elastic deformations of the rear pieces according to the writing pressure applied, the writing tip of the nib, though made of a hard ceramic material, can prevent an interruption of ink feed which would otherwise be caused by an ink viscosity change due to drying of ink or by dried ink scum. Further, if dirt or paper dust adheres to ink paths, the above-described behavior of the writing tip can reliably remove it, assuring a stable writing action. Furthermore, the elastic deformation of the writing tip offers a soft paper-contacting feel and allows the nib to write at any angle to a paper surface and, even if the nib is rotated about the pen axis, at any position on the hemispherical tip portion. It is also possible to draw a line thick or thin by adjusting the writing pressure.
Therefore, a first object of this invention is to simplify the structure of the conical nib to realize a significant improvement in productivity while greatly reducing cost.
A second object of this invention is to improve the conical pen manufacturing process to realize productivity improvements and cost reductions.
A third object of this invention is to provide a ceramic composite conical nib which can enhance a durability of the writing tip of the nib, and also give a writer a smooth writing feel and produce smooth written lines.
A fourth object of this invention is to provide a ceramic composite conical nib which, though the tip of the nib is made from a hard ceramic material, can offer a soft paper-contacting feel and enables the nib to write at any angle to a paper surface and, even if the nib is rotated about the pen axis, at any position on the hemispherical tip portion.
These objects and advantages of the present invention will become more apparent from the following description of preferred embodiments thereof taken in conjunction with the accompanying drawings.